The present invention relates to piezoelectric materials, characterized by comprising certain specific crosslinked polymer compounds having rubber elasticity.
In general, a material generates voltage when imposed on with force or distortion, and vice versa: the phenomenon is called piezoelectric phenomenon or piezoelectric effect.
The materials that show piezoelectric effect (piezoelectric phenomenon) are called piezoelectric materials, and were mainly such inorganic materials as rock crystal and lead titanate zirconate [PZT: Pb(Zr,Ti)O.sub.3 ]. Recently, however, polyvinylidenefluoride (PVDF) was found to show remarkable piezoelectric effect and pyroelectric effect, and since then various other polymer compounds also have actively been studied in their piezoelectric effect, including vinylidenefluoride (VDF)-trifluoroethylene (TrFE) copolymers, polyvinylidenecyanide, vinylidenecyanide (VDCN)-vinylacetate (VAc) copolymers, PVDF based blends with polyurethane, and resin blends based on polyester or polycarbonate which have aromatic hydroxycarboxylic acid residues in their molecular structure. As a result, a number of piezoelectric polymer compounds have been proposed (Japanese Patent Kokai Sho 59-98576, 51-70245, 62-224090 and 48-6297).
The piezoelectric materials hitherto developed, however, are all hard and stiff materials, i.e. inorganic materials such as ceramics and crystalline polymer compounds as mentioned above. Furthermore, these polymer compounds do not show sufficient piezoelectric effect for practical use.